SENT Tuning Boxes

What is SENT?

SENT stands for Single Edge Nibble Transmission, it is new type of data transmission protocol used in some new vehicles. 

Analogue Signals

Previously, the signals from car's sensors back to the ECU were primarily analogue. They usually had a 5 volt range, and could be read quite easily with simple equipment.

At any given moment an analogue signal can be read, the data is simply the voltage. An analogue boost signal it might read 1V at engine idle, and 4V at maximum boost. The following graph gives a good idea of this: 

Analogue signal

This curve starts at 1 volt, and climbs to over 4V as boost increases. The main advantage of this is that it is very simple and the sensors themselves can be very basic. It does however have some major disadvantages:

  • One wire is required for every signal. Even if the sensor incorporates multiple values (for example pressure and temperature, or multiple throttle position tracks) multiple cables back to the ECU are required. 

  • The signal is potentially vulnerable to interference, a change in signal level by +0.1V would result in an increased pressure reading. You can see in the above signal that there is some noise present.

  • The sensor and ECU must be calibrated to each other. 3 Volts might mean 1Bar on one sensor, but 1.5 Bar on another.
  • Minor things like connector terminal corrosion can potentially affect signal level.

SENT Signals

With SENT, the signal type is totally different. Rather than being a simple voltage level representing a value, this is what we now see:

SENT Signal

Each one of these peaks or troughs represents a value based upon how long it is. Putting these together and decoding them allows an encoded message to be deciphered. 

Decoding and encoding these signals is relatively complex. It makes basic fault diagnosis harder without specialist equipment, but the system overall has significant advantages:

  • Many signals can be transmitted on one wire. A Boost sensor can transmit temperature data and boost, or a Throttle pedal can transmit multiple track data down one wire.

  • Very high noise resistance. So long as the signal doesn't drop by enough to make a "1" look like a zero, noise will not affect the signal. If it does, an error will be triggered, rather than the wrong value potentially being accepted.

  • Can directly send a value without prior calibration. Rather Than the ECU needing to know the X Volts = X KPa The SENT sensor can simply send a direct value to the ECU. 

SENT Tuning Boxes

Making tuning boxes for vehicles with SENT sensors is, as a result, significantly more complex than for vehicles with analogue sensors. Here at Bluespark we have developed a quickly growing range of products for vehicles equipped with SENT sensors.

Having a vehicle equipped with SENT technology means that your vehicle cannot be tuned by any traditional tuning box and will require one of our new SENT units.

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